The present invention is directed to the construction of an elevated concrete roadway structure in a number of sections, and, more particularly, it is directed to the construction of a combination box girder and roadway structure where each section is built in a number of stages.
The construction of elevated roadway structures is well known. Such structures may be a simple span between two abutments or it may consist of a structure supported on a number of piers or abutments for instance, where a roadway crosses over a valley. It is not unusual for such an elevated roadway structure to extend for half a mile or more. In the development of highway systems throughout the world, such as the interstate system in the United States, at the outset elevated roadway structures consisted of structural steel girders and beams spanning concrete abutments or piers with a concrete roadway slab supported on the structural steel. More recently, to limit the use of structural steel and to achieve the savings in costs attainable by using all concrete structures, it has been known to span the vertical supports, that is, piers or abutments, with a concrete box girder and roadway structure. Elevated box girder and roadway structures require either a falsework or a truss support for the concrete formwork. While a falsework support extends upwardly from grade to the elevated roadway, a truss support made of structural steel is supported on the upper parts of the vertical supports. In the past the practice has been to construct the entire box girder and roadway slab so that it is formed in a single monolithic pour. Such a procedure requires a very substantial underpinning in the form of falsework or a truss support. While the falsework or truss support is reused for each span or section of the elevated structure the costs of moving and setting up the supporting structure has been considerable.
Therefore, it is the primary object of the present invention to simplify the support structure required to underpin such elevated roadway structures and to effect a considerable reduction in costs both in the materials used and in the time required to set up the support structure.
Another object of the invention is to provide a more efficient procedure for constructing an elevated box girder and roadway structure where work can be carried out on adjacent spans or sections at the same time.